Process for the production of 2,4,5-trichlorotoluene

ABSTRACT

Trichlorotoluene that contains at least 75 percent of 2,4,5trichlorotoluene is prepared by contacting para-chlorotoluene with chlorine in the presence of a chlorination catalyst that is either a metal sulfide or a mixture of a ring-chlorination catalyst and, as co-catalyst, a sulfur compound to form a reaction mixture containing an average of about 3 gram atoms of chlorine per mole and then separating the trichlorotoluene fraction from the reaction mixture.

United States Patent Di Bella [451 Sept. 19, 1972 y [541 PROCESS FOR THEPRODUCTION OF 223,024 7/1959 Australia ..260/650 R2,4,5-TRICHLOROTOLUENE 3,813,371 7/ 1963 Japan...., ..260/650 R [72]Inventor: Eugene E Di Bella Roche-e Park 393,821 4/1964 Japan ..260/6$0R OTHER PUBLICATIONS v [731 Ass1gnee= Tenn Chem Silberrad, J. Chem.Soc., 127, 1925 pp. 2677- 22 Filed: July 31,1970 2684- [211 APPI- 60,083Primary Examiner-Howard T. Mars Attorney-Daniel J. Reardon, Barry G.Magidoff and [52] US. Cl, ..260/650 R Evelyn Berlow [51] Int. Cl. ..C07c25/00, C070 25/04 [58] Field of Search ..260/650 R [57] ABSTRACTTrichlorotoluene that contains at least 75 percent of [56] Rem-macaw2,4,5-trichlorotoluene is prepared by contacting para- UNITED STATESPATENTS chlorotoluene with chlorine in the presence of a chlorinationcatalyst that is either a metal sulfide or a 2 mixture of aring-chlorination catalyst and, as col946040 211934 322 2;; [650 R Xcatalyst, a sulfur compound to form a reaction mixture FOREIGN PATENTSOR APPLICATIONS 988,306 4/1965 Great Britain ..260/650 R 1,116,3531/1968 Great Britain ..260/650 R containing an average of about -3 gramatoms of chlorine per mole and then separating 'the trichlorotoluenefraction from the reaction mixture.

2 Claims, No Drawings PROCESS FOR THE PRODUCTION OF 2,4,5-

TRICHLOROTOLUENE This invention relates to a process for the productionof trichlorotoluenes. More particularly, it relates to a process for thechlorination of parachlorotoluene whereby there is formed a mixture oftrichlorotoluene isomers of unusually high 2,4,5-trichlorotoluenecontent.

2,4,5-Trichlorotoluene is used commercially as an intermediate in theproduction of compounds that are useful as pesticides, lubricants,dyestuffs, and pharmaceuticals. For example, it is used in thepreparation of 2,4,5-trichlorobenzotrifluoride, which is used as aningredient of hydraulic fluids and lubricating composi tions.

In the past 2,4,5-trichlorotoluene has been produced by chlorinatingtoluene or para-chlorotoluene in the presence of iron, iodine, oranother known ringchlorination catalyst to obtain a trichlorotolueneproduct that contains only a relatively small proportion of the2,4,5-isomer and separating this compound from the other, less desirabletrichlorotoluene isomers.

In accordance with this invention, it has been found that whenpara-chlorotoluene is chlorinated in the presence of any of the knownring-chlorination catalysts and a co-catalyst that is a sulfur compoundthe trichlorotoluene mixture formed has a 2,4,5- trichlorotoluenecontent that is substantially higher than that obtained when thechlorination is carried out in the absence of the co-catalyst.

The process of this invention is carried out by contactingpara-chlorotoluene, 2,4-dichlorotoluene, or 3,4-dichlorotoluene withchlorine in the presence of a ring-chlorination catalyst and aco-catalyst as hereinafter defined until the reaction product is amixture of chlorotoluenes that contains an average of about 3 gram atomsof chlorine per mole. This mixture may be fractionally distilled toseparate the trichlorotoluenes from the dichlorotoluenes andtetrachlorotoluenes that are present. The trichlorotoluene fraction,which contains at least 75 percent of 2,4,5-trichlorotoluene, may besubjected to fractional distillation or crystallization to yieldsubstantially pure 2,4,5-trichlorotoluene.

The chlorination of para-chlorotoluene is carried out in the presence ofa ring-chlorination catalyst and a cocatalyst that is a sulfur compound.Any of the wellknown ring-chlorination catalysts that are used in theproduction of chlorob enzenes and chlorotoluenes may be used. Theseinclude, for example, iron, iron chloride, antimony pentachloride,aluminum chloride, zinc chloride, zirconium tetrachloride, tin chloride,molybdenum chloride, iodine, and boron trifluoride. The preferredring-chlorination catalysts and the ones ordinarily used in the practiceof this invention are iron, iron chloride, and zirconium tetrachloride.

The sulfur compounds that may be used as cocatalysts in the process ofthis invention include sulfur and a wide variety of organic andinorganic compounds that contain one or more divalent sulfur atoms andthat are soluble to at least a limited extent in the reaction mixture.These include sulfur, sulfur chlorides, carbon disulfide, thionylchloride, thiophenes, thiophanes, alkyl-, cycloalkyl-, aryl-, andaralkyl mercaptans and dimercaptans, thioethers, and the like. Thesulfur compounds that are preferably used as co-catalysts are sulfur,sulfur monochloride, sulfur dichloride, thiophene, and ethylenetrithiocarbonate.

In a preferred embodiment of this invention, the combination ofring-chlorination catalyst and cocatalyst is replaced by a metallicsulfide. These compounds which contain at least one divalent sulfur atomare sulfides of the aforementioned metals whose chlorides are useful asring-chlorination catalysts. Particularly advantageous results have beenobtained using ferrous sulfide, zirconium disulfide, and zinc sulfide.The metal sulfides may be added to the reaction mixture as such, or theymay be formed in situ by reaction of the metal chloride that is beingused as the ringchlorination catalyst and the sulfur compound that isthe co-catalyst. I

The amounts of the ring-chlorination catalyst and cocatalyst that areused are not critical and are those that will produce a trichlorotoluenefraction that contains at least percent of the 2,4,5-isomer. In mostcases about 0.25 gram to 5 grams of the ring-chlorination catalyst and0.25 gram to 5 grams of the co-catalyst are used per mole ofpara-chlorotoluene. Excellent results have been obtained using either 2grams to 4 grams of the ring-chlorination catalyst and 1 gram to 2 gramsof the co-catalyst or 1 gram to 3 grams of metallic sulfide per mole ofpara-chlorotoluene. The relative amounts of the catalyst and co-catalystthat are used are not critical. Significant increases in the2,4,5,-isomer content of the trichlorotoluene fraction have been notedwhen about 01 part to 5 parts by weight of the cocatalyst was used perpart by weight of the catalyst. In most cases about 0.25 part to 0.50part by weight of the co-catalyst is used per part by weight of theringchlorination catalyst.

The chlorination of para-chlorotoluene, 2,4- dichlorotoluene, or3,4-dichlorotoluene to form trichlorotoluene that contains at least 75percent of the 2,4,5-isomer is carried out by procedures that are wellknown in the art. For example, chlorine may be added to a reactionmixture containing the chlorotoluene, catalyst, and co-catalyst untilthe increase in the weight of the reaction mixture or in its specificgravity indicates that the desired amount of chlorine has reacted withthe chlorotoluene starting material. When the chlorination is continueduntil the reaction product contains an average of about 3 gramatoms ofchlorine per mole, the reaction product generally contains about 75 topercent of trichlorotoluene, 3 to 10 percent of dichlorotoluene, and 5to 20 percent of tetrachlorotoluene. The trichlorotoluene fraction,which may be separated from the dichlorotoluenes and tetrachlorotoluenesby fractional distillation or other known techniques, contains at least75 percent of 2,4,5-trichlorotoluene, the remainder being principally2,3,4-trichlorotoluene. 2,4,5-Trichlorotoluene may be separated from itsisomers by fractional distillation or fractional crystallization.

The chlorination reaction may be carried out at temperatures in therange of about -S to C. with 25 to 50C. the preferred range. Below about5C., the reaction takes place too slowly to be of commercial interest.At temperatures in the range of about 80 to 100C., there is a tendencyfor side-chain chlorinated by-products to form. Since chlorination is anexothermic reaction, external cooling may be required to maintain thereaction temperature in the desired range.

The rate at which chlorine is added to the reaction mixture does nothave an appreciable effect on the yield of trichlorotoluene or on theisomer distribution in the product.

The invention is further illustrated by the examples that follow.

EXAMPLE 1 Mixtures of 253 grams (2.0 moles) of commercialparachlorotoluene which contained 98.4 percent of para-chlorotoluene,0.7 percent of metachlorotoluene, and 0.9 percent of orthochlorotolueneand a chlorination catalyst in a glass chlorination vessel werechlorinated by passing a stream of gaseous chlorine over the surface ofthe reaction mixtures at the rate of about 70 grams per hour until aweight increase of about 138 grams (ca. 2 gram atoms of chlorine permole of para-chlorotoluene) was attained. During the chlorination thereaction mixtures were stirred, and external cooling was used duringmost of the chlorination to maintain the reaction temperature in therange of 25-30C. During the final stages of the chlorination because ofpartial solidification of the 2,4,5-isomer the reaction temperature wasraised to 40-50C. to permit the necessary stirring.

Vapor phase chromatographic analysis indicated that the reactionmixtures contained about 75 to 90 percent of trichlorotoluenes and smallamounts of dichlorotoluenes and tetrachlorotoluenes. The mixtures weredistilled to separate a trichlorotoluene fraction, which was thenfractionally distilled to yield substantially pure2,4,5-trichlorotoluene.

The chlorination catalyst systems used and analysis of the products areset forth in Table 1.

TABLE 1 Comp. Example No. 1A 1B 1C ex.A Catalyst System 2g. 2g. 2g. 2g.ferrous iron iron iron sulfide powder powder powand and der lg. lg.sulfur sulfur monochloride Increase in weight during chlorination (g.)138.8 137.7 136.0 138.5 Analysis of Product (36) 2,5-dichlorotoluene'0.2 0.1 0.2 0.2 2,4-dichlorotoluene 4.5 4.3 5.7 9.42,4,6-trichlorotoluene 2.0 1.5 1.9 9.7 2,3,6-trichlorotoluenc 0.4 0.30.4 0.5 2,3,5-trichlorotoluene' 0.2 0.6 0.5 2,4,5-trichlorotoluene 82.667.4 67.4 44.2 2,3,4-trichlorotoluene 3.7 18.7 18.8 21.32,3,4,6-tetrachlorotoluene 2.6 4.1 2.7 10.6 2,3,4,5-tetrachlorotoluene3.8 3.0 2.4 4.1 I: 2,4,5-isomer in trichlorotoluene fraction 93.1 76.175.6 58.4

Derived from oand m-chlorotolucnes present in p-chlorotoluene startingmaterial.

EXAMPLE 2 Mixtures of 253 grams (2.0 moles) of commercialparachlorotoluene and chlorination catalysts were chlorinated by theprocedure described in Example 1 until a weight increase of about 142grams was attained.

Vapor phase chromatographic analysis indicated that the reactionmixtures contained about percent of trichlorotoluene and smaller amountsof dichlorotoluene and tetrachlorotoluene. 2,4,5- Trichlorotoluene wasseparated from the reaction mixture by the procedure described inExample 1.

The catalyst systems used and analyses of the products are set forth inTable 11.

Derived from oand m-chlorotoluenes present in p-chlorotoluene startingmaterial.

From the data in Tables 1 and 11 it will be seen that the chlorinatedproducts prepared using the catalyst systems of this invention (Examples1A, B, 1C, and 2) contained substantially larger amounts of the desired2,4,5-trichlorotoluene than did those prepared using a ring-chlorinationcatalyst, that is, ironpowder (Comp. Ex. A) or zirconium tetrachloride(Comp. Ex. B), as the sole catalyst. A product having a particularlyhigh 2,4,5-trichlorotoluene content was obtained when para-chlorotoluenewas chlorinated in the presence of ferrous sulfide.

The terms and expressions which have been employed are used as terms ofdescription and not of limitation. There is no intention in the use ofsuch terms and expressions of excluding any equivalents of the featuresshown and described or portions thereof, but it is recognized thatvarious modifications are possible within the scope of the inventionclaimed.

1 claim:

1. The process for the production of trichlorotoluene containing atleast 75 percent of 2,4,5-trichlorotoluene which comprises contactingpara-chlorotoluene with gaseous chlorine in the presence of b. Ferroussulfide in the amount of 1 gram to 3 grams per mole ofpara-chlorotoluene at a temperature in the range of 5 to C. to form amixture of chlorotoluenes containing an average of about 3 gram atoms ofchlorine per mole and thereafter separating from said mixture atrichlorotoluene fraction containing at least 75 percent of 2,4,5-trichlorotoluene.

2. The process for the production of 2,4,5- trichlorotolue ne thatcomprises the steps of contacting para-chlorotoluene with chlorine inthe presence of a catalytic amount of ferrous sulfide at a temperaturein the range of 25 to 50C. to form a mixture of chlorotoluenescontaining an average of about 3 gram atoms of chlorine per mole,separating from said mixture a trichlorotoluene fraction containing atleast 90 percent of 2,4,5-trichlorotoluene, and separating from saidtrichlorotoluene fraction substantially pure 2,4,5- 5

trichlorotoluene.

UNITED. STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3 ,692,850 Dated Sept 19 1972 Inventor(s) Eugene P. Di Bella It is certifiedthat error appears in the above-identified patent and that said LettersPatent are hereby corrected as shown below:

Column 3, line 60, insert an asterisk before Derivecil.

Column 4, line 29, insert an asterisk before Derived".

Column 4, line 55, change b. Ferrous to ferrous Signed and sealed this13th day of February 1973.

(SEAL) Attest:

EDWARD M FLETCHER,JR. ROBERT GOTTSCHALK Attesting Officer Commissionerof Patents FORM PO-1OSO (10-69) USCOMM DC 60376 p69 u.s. GOVERNMENTPRINTING OFFICE: I969 0-366-334

2. The process for the production of 2,4,5-trichlorotoluene thatcomprises the steps of contacting para-chlorotoluene with chlorine inthe presence of a catalytic amount of ferrous sulfide at a temperaturein the range of 25* to 50*C. to form a mixture of chlorotoluenescontaining an average of about 3 gram atoms of chlorine per mole,separating from said mixture a trichlorotoluene fraction containing atleast 90 percent of 2, 4,5-trichlorotoluene, and separating from saidtrichlorotoluene fraction substantially pure 2,4,5-trichlorotoluene.